The subject matter of the present invention relates generally to fuel vent apparatus for venting gaseous fuel vapors of a fuel tank, and in particular to such a vent apparatus which also includes an improved gravity operated valve to prevent liquid fuel spillage from the tank.
The fuel vent apparatus of the present invention is especially useful on the fuel tanks of trucks and other vehicles operated by liquid fuel such as gasoline, diesel fuel and the like. However, it is also useful on fuel tanks for outboard motor boats, lawn mowers, chain saws, etc., to prevent fuel spillage and fires when such fuel tanks are accidentally overturned.
Previously, it has been proposed to provide a fuel tank with a fuel filler cap having a gravity operated valve which closes a vent passsage in such a cap when the tank overturns. However, prior art gravity valves have been provided with weights positioned below the valve members and close the valve only after tipping the tank through a relatively large angle, or in other instances pressures within the tank have caused valves to "stick" in the closed position without providing proper venting. As a result, these valves are slow acting and do not function properly under certain conditions.
In my prior application Ser. No. 2,242, filed Jan. 10, 1979, a gravity operated valve is controlled by a plumb weight which is sufficiently sensitive for closing the valve with very little movement of the tank, e.g. through an angle of about thirty degrees. This apparatus has proved efficacious in many conditions for providing proper venting while preventing fuel spillage from the tank. However, in the case of larger engines where considerable venting of the tank is required, the velocity of airflow can interfere with proper operation of the vent valve. Therefore, it is desired to provide a fuel tank vent apparatus having a vent valve characterized by a positive action, particularly in the case of larger engines having greater airflow.